Numerical Analysis of the Response of Soft Foundation Soils under Tall Embankments and Retaining Walls

Stage construction is an essential method for the building of tall embankments on soft foundation soils. During stage construction, soft foundation soils consolidate and undergo an increase in effective stress, a reduction in void ratio, and an increase in shear strength. However, the combination of soft foundation soil and tall embankments is prone to large settlement deformations and potential failure due to the contribution of lateral movements to vertical settlements. This study documents numerical parametric studies to evaluate failure mechanisms of the mechanically stabilized earth walls founded on soft soils. The number of analyzed parameters was reduced by conducting a dimensional analysis. Analyzed parameters include boundary conditions, soil properties (i.e., backfill friction angle, Young’s modulus, undrained shear strength, Poisson’s ratio) and embankment geometry (i.e., wall height and reinforcement length). Results indicate that decrease in backfill friction angle, increase in embankment height, decrease in undrained shear strength lead, of course, to a decrease in factor of safety, however changes in Young’s modulus and Poisson’s ratio do not contribute to the factor of safety but directly affect the settlements. These results show the limitation of considering allowable stress design and serviceability in the interpretation of large and complex foundation structures.